This seems to be a bug in Filemaker as the layout is not displaying correctly in Webdirect. If there's a corruption in the Theme then repairing the file should fix it - hence why I think it's a bug.
I have attached an image of how it displays in Filemaker, Webdirect 14 and also the file.
The only way I can think of to fix it is to rebuild the entire theme, but this is a massive pain. Any other suggestions?
The main problem is I can't change the tab control elements - for example add a border or reliably change colours.
I also can't create more than one style (as well as Default) - otherwise the styles don't work properly in Webdirect.
When using another theme these features work fine.